Arctic ice cover maximum is fifth-lowest on record

Ice cover in the Arctic reached its fifth-lowest level since 1978; in the south, ice in the Antarctic receded to the fourth-greatest extent since measurements started 36 years ago. What does this say about global temperatures?(Photo : National Snow and Ice Data Center)

Arctic sea ice reached its maximum annual extent on March 21, and the amount measured was the fifth-lowest level ever recorded.

Levels of sea ice in the Arctic have been collected since 1978. Ice levels since that time have shown a decrease in maximums of around 2.6 percent per decade. These numbers are measured in comparison with averages collected from 1981 to 2010.

"Arctic sea ice extent for March 2014 averaged... 5.70 million square miles. This is... 282,000 square miles below the 1981 to 2010 average extent, and... 127,000 square miles above the record March monthly low, which happened in 2006," The National Snow and Ice Data Center (NSIDC) reported.

The term "ice extent" refers to measuring up to the edge of where ice is seen, according to the NSIDC. Area and extent are different measures; each one gives scientists slightly different information. Extent is always a larger number than area, which measures just what is covered with ice.

Ice was significantly lower than normal in the Sea of Okhotsk, located off the east coast of Russia, and the Barents Sea, between Norway and Russia.

The latest the maximum has ever taken place was on March 31, 2010. The maximum this year, 10 days earlier, was the fifth-latest maximum ever recorded. On an average year, that date is around March 9.

In addition to the lack of ice in the north, Antarctic ice in the south receded to the fourth-greatest extent seen in the last 36 years. The summer minimum for that hemisphere was reached on Feb. 23.

The Bering and Barents Seas were both experiencing lower-than-normal ice levels, before an air mass from the northern Arctic moved down, freezing the waterways. This behavior was consistent with what researchers said is a linear decrease in ice levels normally seen at this time of year.

Environmentalists are sounding the alarm that these findings indicate polar ice is disappearing far faster than climate models predict.

"The decline of Arctic sea ice in summer is occurring at a rate that exceeds most model projections," the United Nations' Intergovernmental Panel on Climate Change (IPCC) wrote in its first major report in seven years.

As ice declines in the Arctic and Antarctic regions, melting snow and ice could alter water currents, leading to dramatic changes in the marine environment.

Ice older than a year old continues to get older, according to the study. Multiyear ice is becoming more common in the Arctic. However, the percentage of the Arctic Ocean consisting of ice at least five years or older remains at only 7%, half of what it was in February 2007.

The NSIDC recently released a new Web site where the public may view interactive maps of the Arctic region, information collected by NASA satellites. Using these tools, people can see how the climate has changed in the northernmost region of our home planet. Maps include sea ice, snow cover, surface temperatures, vegetation, water vapor and more.